The objectives of the proposed project is to extend our understanding of the low-temperature renal preservation problem through the use of isolated rabbit kidney as a model. We will verify the reports of kidney survival in the frozen state and systematically optimize the parameters (cryoprotectant concentration, cooling rate, thawing rate) influencing survival as tested by physiological measurements and by transplantation with contralateral nephrectomy. A K ion-Mg ion rich perfusate will be used. Hydroxyethyl starch and dimethylsulfoxide (DMSO) will individually be tested for suitability as renal cryoprotectant drugs. Electronic instrumentation to thaw large organs rapidly will be developed. As an alternate approach to renal cryopreservation, efforts will be made through the use of high concentrations of DMSO to store living kidneys in the absence of freezing.